public class LinkedList {
    class listNode{
        public  int val;
        public listNode next;
        public listNode prev;
        public listNode(int val){
            this.val=val;
        }

    }
    public listNode head;
    public listNode last;



    //头插法
    public void addFirst(int data) {
        listNode node = new listNode(data);
        if (head == null) {
            head = node;
            last = node;
        } else {
            node.next = head;
            head.prev = node;
            head = node;


        }
    }
    //尾插法
    public void addLast(int data){
           listNode node=new listNode(data);
           if(head==null){
               head=node;
               last=node;
           }else {
               last.next=node;
               node.prev=last;
               last=node;
           }
        }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data){
        if(index<0||index>size()){
            return;
        }
        if(index==0){
            addFirst(data);
            return;

        }
        if(index==size()){
            addLast(data);
            return;

        }
        listNode cur=head;
        listNode node=new listNode(data);
        int count=0;
        while (count!=index-1){
            cur=cur.next;
            count++;
        }
        node.next=cur.next;
        cur.next.prev=node;
        cur.next=node;
        node.prev=cur;

    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        listNode cur=head;
        while (cur!=null){
            if(cur.val==key){
                return true;
            }
            cur=cur.next;
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key){
        listNode cur=head;
        while (cur!=null){
            if(cur.val==key) {
                if (cur == head) {
                    head=head.next;
                    if(head!=null){
                        head.prev = null;
                    }else {

                       last=null;
                    }
                } else {
                    if (cur.next == null) {
                        cur.prev.next=null;
                        last=cur.prev;

                    }else {
                        cur.prev.next=cur.next;
                        cur.next.prev=cur.prev;

                    }
                }

                return;
            }else {
                cur=cur.next;
            }

        }
    }
    //删除所有值为key的节点
    public void removeAllKey(int key){
        listNode cur=head;
        while (cur!=null){
            if(cur.val==key) {
                if (cur == head) {
                    head=head.next;
                    if(head!=null){
                        head.prev = null;
                    }else {

                        last=null;
                    }
                } else {
                    if (cur.next == null) {
                        cur.prev.next=null;
                        last=cur.prev;

                    }else {
                        cur.prev.next=cur.next;
                        cur.next.prev=cur.prev;

                    }
                }


            }
                cur=cur.next;


        }
    }
    //得到单链表的长度
    public int size(){
        listNode cur=head;
        int count=0;
        while (cur!=null){
            cur=cur.next;
            count++;
        }
        return  count;

    }
    public void display(){
        listNode cur=head;
        while (cur!=null){
            System.out.println(cur.val+" ");
            cur=cur.next;
        }
        System.out.println();
    }
    public void clear(){
        listNode cur=head;
        while (cur!=null){
            listNode curN=cur.next;
            cur.next=null;
            cur.prev=null;
            cur=curN;
        }
        head=last=null;
    }
}
